The present invention relates to electrical energy storage systems. Electrical utilities normally are engineered to have the capability of producing more electrical power than actually required in their normal peak demand periods. This capability of providing more power, commonly approximately 17% more power, is provided to cover emergency situations.
Power companies face the problem that peak demands have increased dramatically; and since 1985, continue to grow at a rate of 3% per year. It is projected the long period of excess capacity that began in 1974 will come to an end during the decade of 1990. Additionally, environmental concerns have inhibited the building of power plants that would increase the base load capabilities. Power companies have tended to deal with the foregoing problem by installing so called "peaking units" near the areas of large power demand. The peaking units are usually gas turbine-driven generators. Such generators have high capital costs, and additionally, fuel costs for gas turbines are also high.
Various solutions have been suggested to meet the foregoing problem. One solution is to provide an energy storage system of high-efficiency and compactness, and with characteristics that allow it to be installed almost anywhere and in a short time. Several sources have suggested that flywheel storage offers the foregoing desirable characteristics. One such proposal was that of R. F. Post and S. T. Post in the article entitled Flywheels in the December 1973 issue of Scientific American. Some time later in an article entitled Flywheels For Energy Storage appearing in Technology Review, November 1979 (Vol. 82, No. 2, p 32), Alan R. Millner discussed using flywheels for energy storage for peak load shaving on electric utility systems.
More recently U.S. Pat. No. 5,124,605 issued to Bitterly et al discloses a flywheel-based energy methods and apparatus. The Bitterly apparatus has the capacity of storing electric energy as kinetic energy and generating electric energy from the stored kinetic energy. Bitterly et al discloses a system having two flywheels which rotate counterclockwise to each other. The Bitterly flywheels are provided with magnetic bearings as well as liquid balancing bearings and perform within an evacuated, protective housing.
Magnetic bearings are well known in the art and basically comprise a system wherein rotating members are supported by electromagnets. The article entitled Design and Test of a Magnetic Thrust Bearing by Allaire, Mikula, Banaerjee, Lewis and Imlach in the Journal Of the Franklin institute, Vol. 326, No. 6, pp 831-847, 1989 provides an indication of the state of the art of a special type of magnetic bearing as early as 1989.
The present invention is directed to an improved electromagnetic .and magnetic bearing assembly for a stationary flywheel energy storage system. The term stationary refers to a system which is positioned in a given geographic location as contrasted to, for example, flywheel storage systems to be used with automobiles, trucks, buses, or space applications.